hold parts references to prevent deletion

Author: arthurpassos

src/Storages/ExportReplicatedMergeTreePartitionTaskEntry.h

@@ -1,13 +1,21 @@
 #pragma once
 
 #include <Storages/ExportReplicatedMergeTreePartitionManifest.h>
+#include <Storages/MergeTree/IMergeTreeDataPart.h>
 
 namespace DB
 {
 struct ExportReplicatedMergeTreePartitionTaskEntry
 {
+    using DataPartPtr = std::shared_ptr<const IMergeTreeDataPart>;
     ExportReplicatedMergeTreePartitionManifest manifest;
 
     std::size_t parts_to_do;
+    /// References to the parts that should be exported
+    /// This is used to prevent the parts from being deleted before finishing the export operation
+    /// It does not mean this replica will export all the parts
+    /// There is also a chance this replica does not contain a given part and it is totally ok.
+    std::vector<DataPartPtr> part_references;
 };
+
 }

src/Storages/StorageReplicatedMergeTree.cpp

@@ -4443,9 +4443,19 @@ void StorageReplicatedMergeTree::exportMergeTreePartitionUpdatingTask()
             continue;
         }
 
+        std::vector<DataPartPtr> part_references;
+
+        for (const auto & part_name : metadata.parts)
+        {
+            if (const auto part = getPartIfExists(part_name, {MergeTreeDataPartState::Active, MergeTreeDataPartState::Outdated}))
+            {
+                part_references.push_back(part);
+            }
+        }
+
         export_merge_tree_partition_task_entries.emplace(
             key,
-            ExportReplicatedMergeTreePartitionTaskEntry{std::move(metadata), parts_to_do});
+            ExportReplicatedMergeTreePartitionTaskEntry {metadata, parts_to_do, std::move(part_references)});
     }
 
     /// Remove entries that were deleted by someone else